I just read Janice Novak's book "Posture, Get it Straight!" It is the, hands down, best book on the subject I've found so far. She has a knack for simplifying biomechanics and it's filled with great exercises. I can't rave enough about this book. It answered some questions I've had for years, as well as given me hope to change some things about my back that I thought were unchangable.
Her website has some great info also. http://www.improveyourposture.com
I'm going to order her dvds after I get back from vacation. (Unless somebody wants to give me an early birthday present ;)
I'll post a review after I check 'em out.
Do yourself a favor and get this book!
Check out her site at http://improveyourposture.com/